Generally, in a sealed container or a thermal insulator that delivers performance by a high degree of vacuum environment or an inert gas atmosphere having a high purity, such as in a vacuum thermally insulating container, a vacuum thermal insulator, or a plasma display panel, an internal pressure rise brought about by a gas remaining at a time of production or a gas penetrating with lapse of time constitutes a cause of deterioration of the performance of the sealed container or the thermal insulator. Thus, in order to adsorb these gases, a sealed gas adsorption device filled with a gas adsorption material is proposed.
For example, numerous gas adsorption devices are proposed that are applied to a vacuum thermal insulator formed by covering a core material with an outer covering material having a gas barrier property and reducing a pressure of an inside of the outer covering material and that include a gas-adsorptive substance capable of adsorbing an air component, particularly nitrogen which is a hardly adsorbable gas.
These gas adsorption devices have a function of adsorbing and removing a residual gas that is present in an inside of the outer covering material and that has not been removed by an industrial vacuum gas-discharging step, thereby improving thermally insulating performance. However, there is a problem that, when these gas adsorption devices are brought into contact with air before being applied to the thermal insulator, the gas-adsorptive substance adsorbs the air component and the like, and thus a part of the gas-adsorptive substance is consumed.
In addition, in many cases, the gas-adsorptive substance has a property of adsorbing moisture together with the air component. For this reason, an attempt is made to find how moisture adsorption can be suppressed so as to make the gas-adsorptive substance adsorb a large volume of the air component.
For example, as a device for maintaining vacuum within a thermally insulating jacket, there is proposed a device in which an upper-part open container formed of a gas-impermeable material is filled with a Ba—Li alloy exhibiting reactivity to a gas such as nitrogen even at room temperature, and further a dry material powder is disposed in an upper part of the container so as to cover the Ba—Li alloy (see, for example, PTL 1).
This device allows that, because the dry material powder is disposed, moisture adsorption of the Ba—Li alloy is suppressed, and thus consumption of the Ba—Li alloy by moisture adsorption can be suppressed.
In addition, there is proposed a container incorporating a gas adsorption material, having an outer periphery that covers the gas adsorption material and a communication part that does not bring an inside and an outside of the outer periphery into communication with each other when an external force is not applied yet, but brings the inside and the outside of the outer periphery into communication with each other when a predetermined external force is applied (see, for example, PTL 2).
This container prevents the gas adsorption material from being exposed to air and the like by action of the outer periphery. In addition, at a time of use, the inside and the outside of the outer periphery can be brought into communication with each other by application of the external force, and thus gas adsorption can be started. For this reason, this container can suppress consumption of the gas adsorption material, and thus a high adsorption capability can be retained in an arbitrary environment of use.
In addition, there is proposed a gas adsorption device including a gas adsorption material, a barrier container that covers the gas adsorption material, and an air-permeable but hardly moisture-permeable film that covers the barrier container (see, for example, PTL 3).
By this gas adsorption device, suppression of consumption of the gas adsorption material by contact with air can be achieved because the gas adsorption material is covered with the barrier container. Thereafter, in letting the gas in an inside of a thermally insulating material be adsorbed by forming a through-hole in the barrier container, selective adsorption of only the air from the air containing moisture can be realized because the barrier container is covered with the air-permeable but hardly moisture-permeable film. For this reason, it is possible to provide a gas adsorption device with an increased adsorption volume of intended gases other than moisture.
The device disclosed in PTL 1 has a problem that the Ba—Li alloy has a comparatively low capability to adsorb nitrogen, and the adsorption speed is slow. In addition, Ba is a PRTR (Pollutant Release and Transfer Register) designated substance, so that those without a problem to an environment or human bodies are desired for industrial use. In addition, by a structure of covering the Ba—Li alloy with the dry material powder, reach of the moisture to the Ba—Li alloy can be suppressed. However, there is a problem that, because reach of the air cannot be prevented, part of the Ba—Li alloy is consumed.
In addition, in the container disclosed in PTL 2, control of letting the inside and the outside of the container incorporating the gas adsorption material be in non-communication or communication by the external force can be made. By providing the communication at a time point when the communication is needed in an inside of the thermally insulating material, consumption of the gas adsorption material can be prevented. Meanwhile, there is a problem that this control needs the external force, that a cost for imparting a mechanism to the container is needed, and the like.
In addition, there is a problem that, when the residual gas that is present in the inside of the outer covering material and that has not been removed by the industrial vacuum gas-discharging step contains moisture, consumption of the gas adsorption material by moisture adsorption cannot be suppressed.
In addition, in the device disclosed in PTL 3, there is a need to form the through-hole in the barrier container at a time of adsorption of the gas in the inside of the thermal insulator for permeation of the gas. For this reason, there is a problem of increase in a number of manufacturing steps.
Furthermore, the gas adsorption device including the copper ion-exchanged ZSM-5 type zeolite, which is disclosed in PTL 2 and PTL 3, is characterized by having a larger gas adsorption volume and a higher adsorption speed as compared with an already existing conventional gas adsorption device. Meanwhile, in the same manner as in an already existing conventional gas adsorption material, this gas adsorption device adsorbs nitrogen, oxygen, moisture, and the like in the air to be consumed when brought into contact with the air before being applied to the thermal insulator. For this reason, this gas adsorption device has a problem of decrease in the capability to adsorb the residual air that is present in the inside of the outer covering material and that has not been removed by the industrial vacuum gas-discharging step.